A magnetic tunnel junction (MTJ) is used in a Magnetic Random Access Memory (MRAM) to store information. A MTJ typically has at least two magnetic layers separated by a tunneling barrier layer. The tunneling barrier layer allows electrons to tunnel from one magnetic layer to the other. Data storage is achieved by the directional change, from parallel to antiparallel, or vice versa, of magnetic layers in a MTJ.
Information is stored in one of the magnetic layer, which is called a free layer or a storage layer. An important aspect of the MRAMs is to stably store information. However, conventional packaging processing used to form MRAM chips requires temperatures of about 260° C. Exposure of the MTJs to such high temperatures degrades the stability of information stored. This creates information storage stability problems as the embedded MRAM applications often have the MTJs pre-programmed with information prior to packaging.
From the foregoing discussion, it is desirable to provide a reliable MRAM device which can stably store information at backend packaging processing temperatures. This eliminates the high temperature concern for the MTJ element.